The present invention relates generally to providing a voltage to an accessory device and more particularly to an accessory device voltage management system controlled by a host.
A typical measurement probe for acquiring electrical signals from a device under test has a probing head connected to a termination/control box via a transmission cable, such as a coaxial cable. The probing head may be for acquiring voltage or current signals. The probing head has passive and/or active circuitry for conditioning the acquired signal prior to coupling the signal to the termination/control box. The termination/control box has a coaxial signal connector, such as a BNC type connector, and may include power, clock and data connectors for connecting the measurement probe to a measurement test instrument, such as an oscilloscope or the like.
U.S. Pat. No. 6,629,048 B1 teaches a measurement test instrument and associated voltage management system for an accessory device having an accessory device interface that provides a voltage to a memory device in the accessory device. The memory device stores data related to the accessory device, such as the accessory type, power and/or voltage requirements of the accessory and the like. A sensing circuit receives a sensing signal from the accessory device when it is connected to the interface. The sensing circuit generates an interrupt signal that is coupled to a controller. The controller initiates the generation of a clock signal that is coupled to the accessory device through the interface to retrieve accessory device data stored in the device memory. The controller determines if the connected accessory device is a valid device capable of being supported by the measurement test instrument. The controller generates an enable signal for a valid and supported device that is coupled to a voltage switching circuit. The voltage switching circuit generates one or more output voltages that are coupled to the accessory device via the interface to provide power to the accessory device.
U.S. Pat. No. 6,829,547 B1 teaches another measurement test instrument and associated voltage management system for an accessory device. The structure of the accessory device interface is substantially similar to the '048 patent with the accessory device having an memory device for storing accessory data. The measurement test instrument controller functions in a similar manner to the '048 patent to determine if the connected accessory device is a valid device capable of being supported by the measurement test instrument and identifies the voltage requirements for the accessory device. The controller generates an enable signal for a valid and supported device and at least a first voltage code for the identified voltage requirement. A voltage switching circuit receives the enable signal and the voltage code and generates one or more output voltages having the identified voltage requirement that are coupled to the accessory device via the interface to provide power to the accessory device.
The above described voltage management systems require a voltage switching circuit for each interface of the measurement test instrument. Further, each interface requires a sufficient number of interface contacts for coupling the output voltages from the voltage switching circuit to the accessory device. This increases the complexity and cost of the measurement test instrument as well as increasing the cost and complexity of the accessory and measurement test instrument interface. What is needed is an accessory device voltage management system that reduces the cost and complexity of the voltage management system and the interface between the accessory device and the measurement test instrument or host.